The crystal chemical features and occurrence of the new orthoamphiboles (space group Pnmn), protoferro-anthophyllite and protomangano-ferro-anthophyllite, are described. Protoferro-anthophyllites (PFA) are found in fayalite masses from granitic pegmatites at Cheyenne Canyon and Cheyenne Mountain, Colorado, U.S.A. and at Hirukawa-mura, Gifu Prefecture, Japan. Protomangano-ferro-anthophyllites (PMFA) are found in Mn-rich fayalite masses from granitic pegmatites at Suisho-yama, Fukushima Prefecture, and in bedded manganese ore deposits at Yokone-yama, Tochigi Prefecture, Japan. The empirical formulas of PFA from Hirukawa-mura and PMFA from Yokone-yama are (Fe_1.54Mn_0.42Mg_0.14)Fe₅(Si_7.9Al_0.1)O₂₂(OH)₂ and (Mn_1.38Fe_0.59)(Fe_4.1Mg_0.9Ca_0.03)Si₈O₂₂(OH)₂, respectively. The unit cell parameters of PFA are a = 9.388(2), b = 18.387(4), and c = 5.347(1) Å, and those of PMFA are a = 9.425(2), b = 18.303(4), and c = 5.345(1) Å. These minerals are isostructural with synthetic protofluorian-lithian-anthophyllite (Pnmn, Z=2), and have a straight double-tetrahedral chain (O(5)-O(6)-O(5) angle of 177° and 179°, respectively) and M(1), M(2), and M(3) octahedra of regular shape. PFA and PMFA are optically biaxial negative with refractive indices α = 1.690, β = 1.710, and γ = 1.726, and α= 1.695, β = 1.714, and γ = 1.731, respectively. The density (calc.) of PFA is 3.54 and that of PMFA is 3.44 g/cm³. Some PFA and PMFA include fine clinoamphibole lamellae (space group C2/m). PFA may be produced by hydrothermal alteration of fayalite, and PMFA may be similarly produced by alteration of Mn-rich fayalite and also by metasomatism in bedded manganese ore deposits.

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Two Fe-bearing hydrous magnesium silicates, Fe-bearing phase E with the composition Mg_2.22Fe_0.52Si_0.98O6H_2.08, and phase E' with the composition Mg_2.13Fe_0.59Si_0.87O6H_2.52, were synthesized at 14 GPa and 1000°C and studied with single-crystal X-ray diffraction and infrared spectroscopy. The space groups and unit-cell parameters are R3m, a = 2.981(1) Å, c = 13.898(3) Å for Fe-bearing phase E, and P6₃/mmc, a = 2.953(1) Å, c = 14.170(1) Å for phase E'. In addition to the similar compositions and unit-cell parameters, phase E' possesses many structural features characteristic of those of Fe-bearing phase E. Most remarkably, both structures are built of close-packed oxygen atoms along the c axis, with all Si occupying the interstitial tetrahedral sites and M (= Mg + Fe) cations occupying the octahedral sites. All cation sites are partially occupied in both structures. The implausible configuration of M octahedra sharing faces with Si tetrahedra observed in Fe-bearing phase E exists in phase E' as well. The structures of Fe-bearing phase E and phase E', on the other hand, exhibit obvious differences in the stacking sequence of close-packed oxygen atoms, the distributions of M and Si cations between layers of close packed oxygen atoms, and the degree of the M cation ordering. The synthesis and characterization of Fe-bearing phase E and phase E' demonstrate that the phase E-type structures can be rather compliant and complex, and that as we further explore the temperature-pressure-composition space, other types of structures that are similar to or related to the structure of phase E may be discovered.

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X-ray powder diffraction measurements of CaO at high pressure and temperature have been performed using a lever-spring type diamond anvil cell equipped with an external ring heater. The B1 structure transformed into B2 at about 61.2∼63.2 GPa at room temperature during the compression, and the back transformation from the B2 to B1 structure was found at 59.8 GPa during the depression. The equation of states of both the B1 and B2 structures are obtained by Birch-Murnaghan equation. Because B2 structure of CaO is unstable at ambient conditions, the bulk modulus of the B2 structure at high temperature was firstly determined from the P-V-T curve. The B1-B2 transition pressure slightly lowers from 58.8 GPa at 295 K to 53.1 GPa at 685 K, resulting in dP/dT<0. A back transformation from the B2 to B1 structure by depression shows a large hysteresis. The B1-B2 transition highly depends on pressure rather than temperature. Only from the volumes of the CaSiO₃ components, CaSiO₃ perovskite possibly decomposes to SiO₂ (CaCl₂ type) and CaO (B2) in the pressure and temperature range of the lower mantle.

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The profiles of Raiman spectra below 670 cm⁻¹ of synthetic single crystals of forsterite shocked up to 82 GPa were analyzed. Up to the shock pressure of 46.2 GPa, Raman bands of Si-O) external vibrations of translational and rotational modes are linearly shifted without band broadening to higher frequencies with the increase of the residual strain caused by shock pressure. The Mg(M2)-O translational band is not shifted, but broadens linearly with the strain increase. Normalized band shift and broadening are used to compare the variation. These variations show that differential residual stress and strain still remain within cation polyhedra. The dependence of the normalized broadening on the pressures less than 46.2 GPa is formulated, and this relation can be used to estimate the shock pressure of chondritic olivne. Many extra Raman bands are found in this region, implying that the forsterite may be partly transformed into unknown phases.

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A calcium-aluminum-rich inclusion (CAI) containing big palisade bodies was found within the Allende meteorite. The bulk composition and mineral assemblages show that the CAI belongs to coarse-grained Type B. Oxygen isotopic distributions in palisade bodies in the CAI are similar to those observed in typical Type B CAIs, whereas all minerals including melilite in the host parts are enriched in ¹⁶O. The oxygen isotopic distribution in the CAI indicates that exchange of oxygen isotopes in the palisade bodies occurred before the trapping of palisades into the host. The palisade bodies were formed separately as small CAIs in the solar nebula and then accumulated together to form a large CAI. This suggests the possibility that during the CAI formation, O isotopic environment of CAI-forming region in the solar nebula repeatedly changed from ¹⁶O-rich to ¹⁶O-poor.

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Numerous pyrophyllite (“Roseki”) deposits are found in Late Cretaceous volcanic rocks in Chugoku province, Southwest Japan. Judging from mineralogical characteristics, following five types of altered rocks can be distinguished: 1) silicified rock, 2) spotted Toseki, 3) illite-rich Roseki, 4) illite rock developed as a narrow zone and 5) pyrophyllite-bearing Roseki. In addition, clay veins are commonly observable in these alteration rocks. Concentration of various elements including trace elements such as Li, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb and Pb were measured by atomic absorption spectrophotometry. Trace elements such as ⁷Li, ²³Na, ²⁷Al, ³⁹K, ⁴⁹Ti, ⁵⁵Mn, ⁵⁷Fe, ⁶⁹Ga and ¹¹⁸Sn in quartz were measured by a laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). Authigenic quartz in small druse in silicified rocks contain a large amount of Li, Na, K, Fe and Al. Al and Li contents in authigenic quartz vary within 0.01-1.6 wt% and 33-75 ppm, respectively. The Al content of 1.6 wt% in natural quartz is the highest values hitherto recorded in previous papers. These analytical data permitted to establish geochemical characteristics of each altered rocks and the host volcanic rocks. Examining concentration of several elements in relation with aluminum content reveals several significant facts; Li is more concentrated in quartz than that in illite. Average content of K in the altered rocks is rather low compared with that of the host rhyolitic rocks. Elements such as Fe, Mn, Na, Mg, Ca and Zn are contained only in very small amount in the altered rocks. They are lower in altered rocks than those in the host rhyolitic rocks. These observations strongly suggest that main alteration processes of the district were the results of leaching and/or dissolution of the host rhyolitic rocks during the post volcanic hydrothermal activities.

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Potassicleakeite, KNa₂Mg₂Fe³⁺₂LiSi₈O₂₂(OH)₂, the K-dominant leakeite, is found in manganese ore deposit at the Tanohata mine, Iwate Prefecture, Japan. It is monoclinic, C2/m, a = 9.922(5), b = 17.987(7), c = 5.286(2) Å, β = 104.07(3)°, V = 915.1(7) ų and Z = 2. The seven strongest lines in the X-ray powder diffraction pattern are 8.48(67)(110), 4.50(89)(040), 3.40(46)(131), 3.28(45)(240), 3.16(72)(310, 201), 2.83(49)(330), 2.53(100)(-202). Electron microprobe and LAM-ICP-MS analyses gave SiO₂ 55.34, TiO₂ 0.29, Al₂O₃ 0.44, V₂O₃ 5.52, Fe₂O₃ 9.45, MnO 7.81, MgO 7.23, CaO 0.13, K₂O 3.10, Na₂O 8.73, Li₂O 1.2, H₂O (calc) 2.08, total 100.12 wt. %, corresponding to (K_0.57Na_0.46)_Σ1.03(Na_1.98Ca_0.02)_Σ2.00(Mg_1.29Mn_0.65)_Σ1.94(Fe³⁺_1.02V_0.64Mg_0.26Al_0.05Ti_0.03)_Σ2.00-(Li_0.70Mn_0.30)_Σ1.00(Si_7.98Al_0.02)_Σ8.00O₂₂(OH)₂ on the basis of O + OH = 24. It is transparent and reddish brown with vitreous luster. The streak is pale brownish yellow and cleavage {110} is perfect. The fracture is uneven and tenacity is brittle. The hardness is VHN₁₀₀ 425 - 572 kg/mm² (Mohs ∼5). The calculated density is 3.18 g/cm³. It is distinctly pleochroic from yellowish brown to reddish brown. It is optically biaxial positive with α = 1.672(2), β = 1.680(2), γ = 1.692(2), 2V(calc) = 79°, and orientation: b = Z, X^c = +35 to 40°. It occurs as prismatic crystals in veinlets composed mainly of quartz, alkali-feldspars, and serandite. The mineral is considered to be formed under the later stage of hydrothermal activities of contact metasomatism.

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Ktenasite was found as a vein forming mineral in the altered shale of Tamba zone of Jurassic age, at the Hirao mine, Minoo, Osaka, Japan. The mineral was also found in a marginal part of sphalerite in the host rock. This is the first occurrence of ktenasite in Japan. Ktenasite occurred as aggregates of flattened prismatic crystals up to 0.5 mm long and 0.1 mm wide, in association with minerals such as chalcopyrite, serpierite, smithsonite, hydrozincite, and limonite. An EPMA and CHNS/O analyzer gave the empirical formula (Cu_3.446Zn_1.451Co_0.080Pb_0.018Ni_0.007)_Σ5.002(SO₄)_2.003(OH)_5.998·5.99H₂O on the basis of O = 20. The unit cell parameters were a = 5.590(1), b = 6.161(1), c = 23.741(3) Å, and β = 95.628(3)°. The Vickers microhardness was 113 kg/mm² and Moh's hardness was 2.5. The density was 2.93 g/cm³. It is likely that ktenasite at Minoo was formed by a reaction of the Cu-bearing fluids with sphalerite.

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A number of platinum-group mineral (PGM) grains with characteristic optical and geochemical properties are found in the recently discovered PGE-mineralized chromitite at Wadi Hilti in the deeper mantle section of the northern Oman ophiolite. They usually occur as polygonal inclusions within fresh chromian spinel. They have exclusively Ru-Os-Ir compositions with low totals on conventional microprobe analysis and show the same Ru-Os-Ir ratios as Os-rich laurite, (Ru, Os, Ir)S₂, commonly found in the chromitite. Qualitative and quantitative analyses show that oxygen is one of major constituents of these PGM grains, and they are Ru-Os-Ir oxides. They are characteristically lower in Fe-Ni contents than Ru-Os-Ir oxides ever reported. The characteristic radial-fibrous textures as well as a hollow space around the polygons possibly mean their secondary origin with significant volume reduction. The similarity of element ratios and mode of occurrence between the PGE oxides and laurite indicates that the former have been produced by desulfurization/oxidation of the latter. Formation of the PGE oxides from Oman has been performed with an increase of Eh at a very early stage of serpentinization.

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Many studies on melilite group have been carried out in these two decades, and two significant features of the materials have been clarified so far. A number of descriptive and synthetic studies of melilite group have revealed that the compounds are highly tolerant of accommodating various combinations of elements in the structure. Another feature is the incommensurate structure-modulation found in melilites containing Ca as a major element. Structural studies with X-ray diffraction data and a treatment in the five-dimensional space clarified that formation and ordered arrangements of the six-coordinated Ca atoms play an important role to stabilize the long-range order in the modulated structures.

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Lindgrenite, Cu₃(MoO₄)₂(OH)₂, was found in a dump at the Sansei mine, Nara Prefecture, Japan. It occurred as aggregates of thin platy crystals up to 3 mm wide in veinlets in quartz, and as a mono-mineral or in association with limonite, chrysocolla and malachite. It was yellowish green with a greasy luster in hand specimen. The Vickers microhardness was 351 kg mm⁻² (25 g load) and the density was 4.24 g cm⁻³. The empirical formula of the mineral was Cu_2.98Mo_2.01O_8.05(OH)_1.95 on the basis of O = 10. The unit cell parameters were a = 5.620(1), b = 14.043(2), c = 5.041(1) Å, and β = 98.49(1)°. It is likely that lindgrenite at the Sansei mine was formed as a secondary mineral in solutions dissolved from bornite and molybdenite.

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